Weight loss of 5 percent or greater of initial weight is considered clinically significant because it has been associated with improvements in cardiovascular disease risk factors. Lifestyle interventions for obesity are generally effective at producing mean losses of 8-10 percent of initial weight in the short-term. However, sustaining clinically significant weight loss over time continues to be a challenge. Recent analysis from the National Weight Control Registry suggests that sustaining behavioral changes for at least 1 year is essential for long-term weight maintenance and with each specific behavior that relapses, there is an additive risk for weight regain. This is the first study to explicitly make the connecton between behavioral maintenance and weight maintenance. However, given study limitations, it is not clear if this finding generalizes to a more diverse sample with modest weight loss. Previous research has consistently demonstrated that specific behavioral changes are associated with sustained weight loss: reduction in caloric intake, consumption of a low fat diet, moderately vigorous physical activity on most days, and ongoing self-monitoring of weight or dietary intake. However, determinants of maintaining these behavior changes have not been studied. Establishing behavioral maintenance as a key feature of long-term weight maintenance and identifying predictors of sustained behavioral change, may inform refinement and tailoring of lifestyle interventions for obesity to achieve sustained, clinically significant weight loss. Ths project makes use of secondary data to study the association between sustained behavioral change for 1 year or more and successful long-term maintenance of clinically significant weight loss, and to identify predictors of sustained behavioral changes using data from the NHLBI-funded PREMIER and Weight Loss Maintenance (WLM) Trials. Both of these trials are randomized multi-center behavioral clinical trials that included an intensive behavioral lifestyle intervention in the first six months, had a maintenance phase (12 months in PREMIER, 30 months in WLM), collected long-term weight, behavioral, and psychosocial data, and featured large multi-ethnic samples of overweight/obese adults. We plan to pursue two specific aims using latent class analysis: 1) examine the association between sustained behavioral change for 1 year or more and successful long-term weight maintenance; and 2) identify determinants of sustained behavioral changes that promote long-term weight maintenance. The innovation of this project includes the redirection of focus from weight to modifiable behavior. The significance is that a better understanding of factors associated with sustaining behavior changes could help to tailor lifestyle interventions to achieve broader success with long- term weight maintenance in diverse patient populations.